Questions and Answers
What is an incorrect method to reach ZAV?
What is a characteristic of ZAV access?
What is true about accessing ZAV?
What is a limitation of ZAV?
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What is not a method to access ZAV?
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What is false about ZAV?
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What is a restriction on accessing ZAV?
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What is not possible with ZAV?
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What is a limitation on ZAV accessibility?
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What is not a characteristic of ZAV access?
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What happens to the air voids in a compacted soil sample when it reaches its maximum degree of compaction?
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What is the significance of achieving a degree of compaction where all air voids are removed?
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What would be the likely effect on the compaction curve if the soil sample is not fully compacted?
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What is the primary cause of entrapped air in a soil sample during compaction?
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Which of the following would NOT affect the compactive effort required to achieve a certain degree of compaction?
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What is the purpose of the Standard Proctor Equipment in soil compaction testing?
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How does the presence of entrapped air affect the dry density of a compacted soil sample?
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What happens to the compaction curve when the soil sample is over-compacted?
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What is the effect of increasing the compactive effort on the dry density of a compacted soil sample?
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What is the significance of determining the maximum dry density of a soil sample?
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How many times is the soil compacted for each lift in the Modified Proctor Test?
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What was the Modified Proctor Test developed during?
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What is the primary purpose of compacting a soil sample?
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What happens to the dry density of a compacted soil sample when it reaches its maximum degree of compaction?
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What is the effect of entrapped air on the dry density of a compacted soil sample?
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What is the significance of the Standard Proctor Equipment in soil compaction testing?
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What happens to the compaction curve when the soil sample is over-compacted?
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What is the effect of increasing the compactive effort on the dry density of a compacted soil sample?
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What is the primary cause of entrapped air in a soil sample during compaction?
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Why is it important to remove all air voids from a compacted soil sample?
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Study Notes
Compaction Process
- The compaction process is assumed not to decrease the volume of solids or soil grains.
Effects of Compaction
- Increases shear strength, density, and bearing capacity of soil.
- Allows for larger loads to be applied to compacted soils due to their increased strength.
Mechanism of Compaction
Cohesive Principles
- Interaction between adsorbed layer and interpretable force.
- Breaking up of old bonds and establishment of new bonds between particles.
- Bending and distortion of soil particles.
Cohesionless Principles
- Rearrangement of soil grains.
- Breaking up of some cementation.
- Bending and distortion of soil particles.
Theories of Compaction
- Lambe theory: physico-chemical concept.
- Proctor theory (1933): lubrication theory, where water addition causes a thin layer to be absorbed by soil grains, increasing the layer with more water.
Role of Water in Compaction
- Water lubricates soil grains (cohesionless soil), allowing them to slide easily and achieve a denser arrangement.
- Water expansion of the double layer, leading to a more orderly arrangement of particles, resulting in higher density (clayey soil).
Phase Diagram
- For a given water content w, the maximum density (ZAV) cannot be reached by compaction.
Soil Compaction
- Objective: increase density, strength, bearing capacity, and reduce permeability and compressibility
- Laboratory work: obtain maximum dry density and optimum water content
- Field compaction: executed by contractors using rollers and compactors
Compaction Process
- Definition: increasing soil unit weight by reducing the soil void ratio using mechanical devices
- Modified Proctor Test: compacting soil in five layers with a 10 Lbs hammer, 18 inches drop height, and 25 blows/layer
- Modified Proctor Energy: 56,250 ft-lb/ft³, calculated by (25 blows/layer) * (5 layers) * (10 lbs) * (1.5 ft) / (1/30) ft³
Comparison of Standard and Modified Proctor Tests
- Mold size: 1/30 ft³ for both tests
- Standard Proctor Test: 12" height of drop, 5.5 lb hammer, 3 layers, 25 blows/layer, and energy 12,375 ft-lb/ft³
- Modified Proctor Test: 18" height of drop, 10 lb hammer, 5 layers, 25 blows/layer, and energy 56,250 ft-lb/ft³
Compaction Procedure in Lab
- Method: removing air voids to achieve a degree of compaction (S=1)
- Water content: wW / vt vw
Soil Compaction
- Objective: Increase density, strength, bearing capacity, and reduce permeability and compressibility
- Laboratory work: Obtain maximum dry density and optimum water content
- Field Compaction: Contractors use rollers and compactors to achieve compaction
Compaction Process
- Definition: Increasing soil unit weight by reducing soil void ratio using mechanical devices
- Reduces permeability and compressibility
Modified Proctor Test
- Similar to Standard Proctor Test with exceptions:
- Soil compacted in five layers
- Hammer weight: 10 lbs or 4.54 kg
- Drop height: 18 inches or 45.72 cm
- Calculated energy: 56,250 ft-lb/ft³
Standard Proctor Test
- Mold size: 1/30 ft³
- Drop height: 12 inches
- Hammer weight: 5.5 lbs
- 3 layers
- 25 blows/layer
- Energy: 12,375 ft-lb/ft³
Compaction Procedure in Lab
- Method: Drop hammer 25 times onto confined soil
- Soil divided into three lifts, each compacted 25 times
- Done 4-6 times from dry to wet
- Goal: Achieve maximum dry density and optimum water content
History of Modified Proctor Test
- Developed during World War II
- By the U.S.
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Description
This quiz covers the effects of soil compaction, including increased shear strength, density, and bearing capacity. It explores how compaction enables larger loads to be applied to soils.